Electrical condenser



Vv. H. PRESS July 1, w24.

ELECTRICAL CONDENSER lllllll ELECTRICAL CONDENSER 3 Shees-Sheet 2 Filed Dec.

NV. H. PRESS ELECTRICAL CONDENSER Filed Dec. 5. i921 I5 SheeS-Sheet 3 .meestal ELCTICAL CNDENSE-l,

epplication filed Eecainner 5, i921. Serial En. 519,8S9.

To all who/1n t may concern:

Ee it known that l, TvViLLieir H. Pninss, a citizen of the United States of America, end e resident of Belmont, State of Messschusetts, have invented certain new and useful Electrical Condensers, the principles of which are set forth in the following specification und accompanying drawings, which disclose the form of the invention which l new consider to he the hest ot the various forms in which the principles ot the invention nl sy he embodied.

This invention relates to electrical condensers. y Condensers embodying ,the present invention are for use generally, but in particular may' ne used es en element in dummy antennee end redio frequency reservoir circuits, ss series antenne condensers und also for other ,radio uses where large amount ot energyY is handled in e radio frequency circuit of low resistanceu is en exemple ot e practice-l and commerciel embodiment of such a condenser, it may he made in s standard size of .O02 ini'd., capable of withstanding en effective voltage of 15,000, and e, current of 'nine smperes et 3,000 meters maximum, alt-ho it is to' he understood that the general principles of this invention are applicable to condensers of other sizes end electrical characteristics. rllhe types of condensers asV embodied in the present invention. are known as mica condensers, inasnnicli es thej,7 usually comprise stacks composed of alternate sheets iioil and dielectric, the foil consisting preferably or" e soft mete-rial such :is lead or tin, end the dielectric consisting preteruhly `of mice, which is one of the best dielec-l trics known for this purpose. The stacks are constructed in sections'connected in series with separators between the sections in e, well-known manner, and are clamped and se'cured within suitable cesings, the case ing gree-ruhly in service constituting one of the terminals ot the condenser und the other terminal projet? g thru the casing;r end inf suletcd thereil lt has been toin'id that the hysteresis losses in e, mice condense` in general increase very rapidly with increased tempereture ot the mice which results in operating the ycondenser with the mica at en undesirelole point-'m2 its phese ongle temperature curve. A stsclf oi e mice condenser coinprising the e-ltemete sheets ot vfoil and dielectric end in e wax filler,.or which has been treated with some suitable wax such es psren and embedded in sucli perathn, has very low thermal conductivity und therefore under loa-d the heut generated is not properly conducted from the stack, which results in high temperature rise of the stack. rlhis is further accelerated by the hysteresis losses in mice, producing heet,

4which still lurt ier increases the tempereture, (the proce-ss beingcumulzttive,) and limits the leed that the condenser might curry continuousl;7 to comparatively low velue. rlhe thermal path thru a condenser of this type depends on the eres of the mice sheets und on the length of the stack; that is, the length in direction at right angles to the plane of the she-ets.

ein object o' the present invention is to proviee e condenser in which the heet conduction and radiation. 'from the steel; or stacks is et e maximum, wl'ierelov the stocks are meinte-ined et e minimum temperature for a given lood, which results in the de sirehle operation and efficiency of the condenser, und e comparatively smell volume of mics for n given load when compared with existing designs.

Another object of the invention is to provide e construction which permits maximum loading of the condenser without unduly heating the seine.

Aeinother object of the invention is to provioe ineens for allowing the expansion of the ,insulating filler or emhednient in e oondenser.

ln general, the objects shove enumera-ted are obte-ined hy utilizing in e condenser of any given electrics-l clnuecte-ristics e plurality of stacks ot optinnun lengthfor heet conduction instead of' e single stack ci u length. required to produce e condenser to withstand given voltage and for e given capacity..

The stack snould have minimum length for obtaining the maximum heet conduction and radiation therefrom. This length, however, in e series section condenser heving ends et ev difference lot potentiel should be such that the creepsge path between the ends of the stack is at a sate minimum length. ln other words, in this design the minimum stach length that can safely be used for creepagc for the voltages employed is incorporated in the design. The stack has a maximum thermal conductivity to the casing and tio the highpotent ial terminal.

In the accompanying drawings, l have, illustrated one. embodiment of the invention, in which p Figure 1 is a sectional plan View of the condenser;

Fig. 2 is a sectional elevation thereof; and

Fig. 3 is a sectional plan View thereofen line 3 3 of Fig. 2, looking in the direction of the arrows.

In the design ol condensers v'for a given voltage and capacity, it is necessary to have the mica and foil sheets of such size that when the sections composing the stacks are connected in series or series parallel, such stacks will have the correct capacity and be capable of withstanding a given voltage. ln the present embodiment cf the invention, the condenser comprises a plurality of stacks S, for instance four in number as illustrated. llhe several stacks are connected in parallel to a central terminal 1 and the casing 2,

-which is preferably of metal. Each stack S consists of a plurality of sections connected in series with separators inserted between the sections and projecting beyond the connections in the usual manner. These stacks in turn are connected in parallel, the outer ends ot' the stack being electrically connect ed to the casing 2, and the inner ends of the stack being electrically connected to a metal block or pressure member 3, having high thermal conductivity compared with the total conductivity of the stacks in contact therewith. The metal block 3 is preferably of some light metal such as alm'niuum, and in 'the present embodiment is a cube having flat surfaces engaging the inner ends t' the stacks S as indicated at 4. Each stack secured in position and clamped within the casing 2 against one face of the hlock 3 by means of a metal pressure plate 5 engaging the outer end of the stack, and with which a screw G threaded thru the casing engages. It will thus be seen that each stack S is compressed between the block 3 and one of the pressure plates 5. 'lhe block 3 covers substantially the entire surface. ot' the inner lnd of each stack, while each pressure niember 5 does the same. at. the opposite end of each stack- S and preferably consists of a good conducting mcta'l which is electrically and conductively connected to the casing. The stacks S as here disclosed are arranged horizontally within the casing; that is` the. individual slit-ets composing tht` stack are at right angles to the base. The free terminal ot' the innermost section ot' each stack has soldered to it a flexible copper lead 7 (Fig.

1) which' is bent back around the end of the stack and interposed between the stack and the block 3, while the free terminal of the outermost section of each stack is in like manner provided with a copper lead 8 which is bent back and clamped between the pressure plate 5 and the stach, whereby the inner ends of all the stacks are electrically and conductively connected to the block 3, while the outer ends of the. stacks are electrically and conductively connected to the casing 2. In positioning the several stacks S in the condenser casing and clamping them in position, the free terminals of the innermost sections of adjacent stacks should be positioned adjacent to each other as indicated at 9, these points being at the same potential and not requiring any insulation between them. Threaded thru the block 3 and secured in place by a lnut located in a recess in the lower end of theblock 3 (Fig. 2) is the terminal 1 which projects outwardlv thru an opening 10 at the top Vof the casing at the side thereof remote from a closure 'or bottom 11. This terminal 1 has high thermal conductivity for properly conducting the heat transmitted from the stacks S to the central member 3. In this invention, there is provided a plurality of relatively short stacks havin good thermal contact with members of hlgh thermal conductivity at opposite ends, which members have adequate radiating surfaces exposed to the air. Inasmuch as the high potential terminal 1 Amust be thoroly insulated from the cas-0 ing 2, which is the low potential terminal, I utilize an insulating device 12. In the present embodiment, this insulating device comprises a disc or plate 13, of insulating material, which is of an area greater than the area o f the opening 10 within the casing and extending over the boundaries of said opening. This disc is preferably of some material having high insulating qua ities and low loss such as mica, and should e so designed as to withstand the ditferene in potential between the casing 2 and terminal 1. lt is preferred that this plate`13 consist of mica, which is o-ne of the bestl materials for this purpose,this plate 13 being clamped inwardly of its edge to the casing 2 by means of a metal ring 14 and screws 15 passing thru the ring 14 into the casing 2, a suitable lead or other gasket 16 being interposed between the mica sheet and the casing 2 to secure a tight joint. The member 1 eX- tends thru the disc 13. Mounted around member l below the plate 13 is an insulating bushing t7 of reduced diameter compared to plate i3 and engagingr the bottom of disc 13 and surrrnnuli-ng terminal 1. This bushing is provided with one or more corrugations or grooves 18 arranged circumferentially. thermo-ouml to increase the creepage distance between the terminal tand casing 2,

llt?

and consists preferably of a laminated structure; for instance, a plurality of mica pieces or discs of diameter reduced compared with the disc 13 and compressed together in the manner hereinafter described. Upon the Opf' side of the large mica plate 13 is an insulating bushing' 1S) of reduced diameter compared with disc 13 mounted thereon and surrounding and insulating the upper pors oi, the member l. Like the bushing 17, bushing 19 is also of laminated' insulatmaterial preferably builtl up of superimposed pieces or discs of mica and of decreasing diameter upwardly as illustrated, orniing upwardly tapering bushing.

The device 12 is preferably constructed or assembled on member 1 .by assembling thereon the mica discs, plates or washers in their proper order.I In the embodiment herein illustrated, nutv 20 is threaded on member 1. The mica Washers or pieces constituting the bushing 17 are then positioned or assembled on member 1 upon nut 20,then disc 13 is positioned, andthen the pieces constituting the bushing 19 arepositioned ou member A, Washer 21 and round nut 22 are then threaded upon the upper end of member 1 to hold the mica'sheets and pieces against dislocation. The assemien treated in a bath of hot molten ng material, which vvill act more or less as an adhesive, for about fifteen minutes until bubbles cease, eitherwith or With-k Suitable materials for this purpose are insulating ,ftYai-iiishes, such as paraiiin or fusible insulation such as sulfur. rlhe assembly While hot and impregnated With molten insulating material is compressed or clamped tightly by nut 22 and allowed tocool, thus clamping the mica sheets together in a solid mass out the application of vacuum'.

held together by nut 22 (which may bepinned to member 1) and by the fusible insulation which has non7 solidihed. The bushing i9 is then cut, turned or ground to proper shape and polished, providing a smooth tapered sur-'face 23. The bushings 1T and 19 are thus retained and supported on plate 13 and held` under compression entirely by means of member 1 and nuts 2O and rThe grooves 1S are formed by assembling intermediate mica. Washers oi' reduced diamove nut 22, in close electrical Contact erewith und member t, is a concavo-conmetal 'member 2i, having its concave side facing the bushing 19 and having its edge 26: in vertical alinement with and spaced from the. clamping ring llt. The inination of the surface 223 ot tie bushing and the curvature and spacing ot the member' 24; are so arranged with reference each other and so proportioned that any A erence of potential between the opposite ends ot the Amember 1 produces electrical stresses not thru the insulator 19 but mainly thru the air from member 24 to the casfor the insulating device 12, preventing deterioration thereof; that is, 1t 1s located above-the insulating disc 13 and the bushing 19.' Mounted on terminal 1 above the concavo-convex member 24 is a largc-areaed radiating bell-shaped brass member 27 eX- tending out beyond the member 24 and enclosing the same `and adapted to efficiently radiate the heat conducted from the stacks by terminal 1. The corona member 2t and r-adiatin member 27 are secured in place by means o a nut 28 threaded upon the upper portion of the member 1, and above this are located washer 29 and -nut 30 whereby any suitable lead may be attached to the high potential terminal in the usual manner.

I have also. provided a spark-gap for association With the condenser to prevent the formation of excessive differences of potential between the high and 10W potential portions thereof. For this purpose, the metal member 2d is struck down, forming a vertical part 31, on which is mounted a roundended spark-pin 32 having a longitudinal slot 33 therein and secured to part 31 by `means of a screwand nut 34 extending thru slot 33', whereby the spark-pin 32 may be adjusted vertically relative to the clamping ring 14 to increase or decrease the distance between them, the'piu 32 being in vertical alinement with such ring and forming therewith a spark-gap.

By means of the four adjusting screws 6, the central pressure member 3 may be adjusted back and forth Within the casing along lines at right angles to cach other to properly position terminal 1 within the casing and with reference to the opening l0, the stacks S being arranged C apart around the terminal 1 as a center and engaging the vertical t'aces of block El, two stacks being arranged on each line, engaging opposite faces of block 3 and adjustable baci; and forth With member' 3 by means or" their screws 6. This adjustnientmay be secured when the stacks S are assembled with- Iin the condenser casing 2, and .uponV final Adjacent stacks S are arranged at right llO angles to each other forming an angle between each pair which the sections connections face, four such angles being formed ,A outer ends of the stacks are at the potential of the casing, being electrically connected thereto. Hence the casing may be very close to the outer ends of the stacksybut must be increasingly spacedfrom the stacksl towards their inner ends as the potential increases from the outer end to. the inner end of each stack. By reason of the angles formed between adjacent stacks, the casing is reduced in diameter or in cross section at these points along lines bisecting the angles, and projects into these angles as indicated at 85, the inner walls of the casing, however, being increasingly spaced from each stack towards its inner end on account of the increased potential diiierence between the casing and inner portions of the stack. By the above construction, is provided a casing having minimum volume and weight and a condenser having a resulting minimum of ller and a maximum thermal conductivity between the stack and casing via the filler path but in which all parts at a Vdifference of potential are sufficiently spaced for insulating purposes and in accordance with the potential gradient.. By reason of the arrangement of stacks herein described and reduction of the size of the casing in accordance with the potential gradient, the casing having minimum clearance at all points, the casing in cross section is a more or less cross-shaped or what may be called a clover leaf shape.

Arranged at diagonally opposite points on the outside of the casing 2 centrally thereof are projecting integral metal horizontal anves 36 constituting securing lugs for mounting thecondenser in or on any suitable rack. These flanges adjacent the vertical portions of the casing are provided with openings 37 to allow air-circulation for cooling purposes. The reduced portions 35 of the casing 2 also perform an additional function, inasmuch as when two condensers are assembled in contact as indicated in broken lines (Fig. 1), there is provided be-l above described and as shown in the draw-Y ings, the stacks and the high potential terminal are embedded or surrounded with insulating material W, such as paraiin or oil. This embedment is preferably secured within the condenser thru the bottom, the latter comprising a removable closure 11 of special construction for a purpose hereinafter described. This closure preferably consists 'of a box-like member 38, having airpassages 4:0 therethru, and a flexible metal diaphragm 41 having centrally thereon cor.- centric corrugations 42, secured at its edge to member 38 by screws 43, which also secure closure 11'to casing 2 with diaphragm 41l innermost, and forming with member' 38 a box having a chamber Located within a chamber 44 and bearing against the diaphragm is a spring 45, which maintains the diaphragm 41 yieldingly in elevated position relative to the bottom of the casing.

It, for any reason, during the use of the condenser, the wax or oil embedment W should expand, this expansion reacts against the diaphragm il-1, which yields compressing the spring 45 without straining the casing 2 and thus relieving the latter from stress or distortion due to the expansion of the embedment whereby the several stacks S are maintained under constant compression of a high order without variation, change of capacity, or deterioration due to expansion of the casing and subsequentI loosening of the clamps of which the casing forms a part.

The stacks S of the present invention may be constructed and assembled in part inthe manner described in my coperiding application Serial No. 456,903, filed March 30, 1921.

The process therein described covers the manufacture of a stack by preliminarily dippingthe individual sheets of mica in suitable insulating material, such as molten parafn, and building what is called the material stack consisting of alternate sheets of foil and dielectric, and then treating the material stack thus formed in molten insulating material such as paraffin and apply-ing high compression and cooling, forming a solid block. After this, the material stack is split upinto sections, which are connected in series, and the insulating separators inserted between the sections. Of course, the sections may be assembled and connected by any desired method. For

instance, each section may be built up under molten wax, heated, compressed and cooled under pressure. Each section is then tested for capacity and volt-age. The sections are then connected in series and separators inserted between them. After the sections have been connected by solder and the sectional separators positioned, the two leads 7 and 8 are soldered to the free terminals of the end sections. The stack is then placed on the base Qt a building stand provided with four vertical rods having vertical notches upon their inner sides adapted to receive the corners of the condenser stack; or, it' so desired, a stand having six rods may be used, two rods' engaging each side of the stack and one at each end, A stand adaptable for'this purpose vis disclosed in a pending application of 'Gn lV. Pickard, Serialy No. 330,919, filed May 12, 1920. The

the present construction, the insulator 12 comprises a single mica disc 13 clamped to the casing 2,andbuiltup discs of mica of reduced diameter forming bushings upon and supported by the disc 13, the bushingsbeing clamped to the disc 13 atopposite sides thereof by means of the member 1 and cooperating nuts threaded thereon.

By the present invention, instead of using one stack, I have used four stacks. each stack having a minimum length consistent with the creepage between the oppositelends of the stack due to voltage differences. Each stack has maximum'thermal conductivity to the casing and to the high potential terminal. The high potential terminal is provided on the exterior of the condenser with a corona spark-gap shield and a large heatradiating member, the casing 2 constituting the other large heat-radiating member. It will thus be seen that each stack, of niinimum length, engages at opposite ends conductors having a high thermal conductivityy and large heatiradiating powers. The construction and method of buildingthe stack is such that side slip is prevented. The pres- `sure vapplied to the opposite ends of each stack should be of the order of thousands of pounds per square inch. and of an order which is slightly below a value that will, cause spreading of the foil. The structure above-described is such that the stacks are maintained at a minimum temperature for a given load, which results in efficient opere tion and low loss. In this invention, by placing four short stacks, which are electrically in parallel with one 'another and each consist-ing of series sections, thermally parahel between high-conducting terminals. the thiermal path is improved in a ratio of approxh mately sixteen to one over a single stack having the same electric-al characteristics and built with the same size of mica.. In

this arrangement,v I have improved the coudenser construction by increasing the thei-- mal conductivity and radiation of the structure so that it will carry several times the energy of the equivalentsingle stack with the same heating. In the present in vention.

for the same capacity, I have been able tol reduce the amount of mica required in a condenser, thus materially reducing the cost.

For instance, in a condenserhaving a`single` stack of the same length as the total length of the four stacks of the present condenser and having the capacity of the condenser of the present invention, there would be required mica sheets of four times the area overy those required for the condenser of this invention. Furthermore, a muclrmore exexpensive clamping means would be required'toobtain th(` same pressure per unit area, this clamping means moreover would be inferior and iiietiicientas well as bulky. In the ,present invention, by the methods of ent invention provides a very efficient high in which the stacks are maintained under the highest practicable compression to maintain the sheets of foil and dielectriein intensionvcondenser which is very compact,

tiniate contact to prevent losses in the stackV and increase its thermal conductivity, at the same time the casing being so constructed as to have a high heat-radiation from the outer ends of the stacks and which is sufficiently spaced for insulating purposes from points along the several stacks at a difference of potential without unduly increasing :the size of the easing. TheI in- 'ner ends of the stacks, in like manner, have high thermal conductivity to the outside thru block Band terminal 1, where the heat is radiated by the large heat-radiating niembers upon the terminal 1. Altho the Whole condenser is embedded in Wax, the pressure is maintained constant. on the stacks irrespective of the expansion of the wax embedment. b v reason of the flexible. diafragm and spring box supplied to allow expansion. taking the strain ofll of the clamping portion of the casing.

lnasmuch as in quantity production it is advisable to have the blocks 3 and casings ot' uniforin'standard sizeain cases where the stacks S arey too short to be properly lOtl clamped between such casiiigs and blocks.

additional metal blocks not illustratedl may be inserted between the inner ends ot the stacks and `blocks 5l to secure the required `iressure and clampiigigvthese additional blocks forming with blclsfahighl v thermal conductive path to terminal 1 and constituting with blocks 3 the central pressure member.

It is to be understood that the invention is not limited to the embodiments and features specifically shown and described herein. but that such embodiments and features are subject to changes and modifications without any departure from' the spirit of the invention.

The word plurality is used herein to detine two or more stat-ks. as the case may be.

I claim:

I. An electrical .'ondenser comprising a pluralit)7 of stacksrof sheets each of which stacks isshort for heat conduction as compared with a single stack' electricalliY equivalent to the plural stacks: a common enclosure for said plural stacks; two heat-v ralit).v ot stacks to one'of said lieat-radiat'- Y ing members; the other set of electrical ends 4the two radiators.

of said plural stacks beingl thermallyl and electrically. connected to the other of said heat-radiating members, whereby said 'plu-I ral stacks are connected in parallel between 2. An electrical condensei` comprising :L plurality of stacksof sheets each of which stacks is short for'heatconduction as compared with a single stack electrically equiv alent to the pluralityl of stacks; a common metal casing for all said short stacks and with which as a heat-radiator and condenser terminal one set of electrical ends of 'saidv plurall stacks is in good thermal and electrical connection; heat-radiating and .terminal means mounted externally on and elec- ?trical insulated from said metal casing; `and -therma-l and electrical conducting means eX- tending between the other `set of electrical ends of said shortplural stacks and said external radiating means,- and electrically insulated from said casin l 3. In an electrical condenser,- a casing, a

' .plurality of stacks arranged-withinthe casing, a commonf metallic .pressure member engaging the inner vends of the stacks, adjustingV means mounted on the Casing, and engaging the outer ends of the stacks whereby said pressure member may beadjusted along lines at an angleto each other, and a terminal connected to said pressure member and projecting'` thru the casing.

4. An electrical' condenser comprising a 'n pluralityof stacks of sheets, each stackl being short for heat-conducting as compared with a single stack electrically equivalent to said plural stacks.; a metal casing for said pluralstacks and constituting one 'terminal of the condenser; a second condenser terminal projecting out through and insulated from said metal casing; each of said stacks consisting of a plurality of serially-connected sections and said plural stacks being connected in parallel between said two condenser terminals;v a central 'met-al block against which abut one set of ends of said plural stacks which radiate outwardly from said block toward the walls of said casing: said block being thermally and'electrically connected to saidl projecting condenser4 terminal; and thermal and electrical connecting means between the outer ends of the stacks and said-metal casing, said connecting means comprising devices which clamp each stack of serially-connected sections against said central metal block.

5. An electrical condenser comprising a radiallyfrom said central'metal block; a

metal casing' enclosing 'said stacks and elecl trically and thermally connected to the outer ends of the stacks, and constituting a condenser terminal and heat-radiator; a terminal lead extending from said-.central metal block out through and insulated from said.metal casing and constituted to conduct heat fromsaid block; and a heat-radiator mounted on said terminal lead outside the metal casing.

A6. In an electrical condenser, a casing, a plurality of stacks 'within the casing, a centrally-located pressure member with which the inner endsof the stacks engage, pressure members engaging the outer ends ot the stacks, means threaded in said casing and engaging said last-mentioned pressure mem bers for .compressing the stacks against `the central member, the outer ends of said stacks being electrically connected to the casing and the inner ends electrically connected to the pressure member, and a rigid terminal secured to said pressure member and extending thru the casing to the outside thereof, 'and means insulating said terminal from said casing.

7. In an electricalcondenser, a plurality thereof and provided with four vertical surv faces, four stacks arranged horizontally within said casing and having their inner ends engaging said surfaces, said stacks being arranged along lines. at right angles to each other, threaded members engaging the casing and outer ends ot the stacks 'for compressing the same against the central member, the inner ends of said stacks being electrically connected to the central member and the outer ends of the stacks being electrically lconnec-ted to the casing. and a terminal connected to said central member, having a high thermal conductivity, extending outside of the casing and insulatedtherefrom.

9. In an electrical condenser. a metal casing, a block arranged centrally within said casing and having vertical sides, condenser stacks arranged horizontally within the casing and each engaging one of the sides, said stacks each comprising sections connected in series, the inner ends of the stacks being elecl the angles between the stacks and shaped to provide increased separation between the casing and adjacent portions of the stacks in accordance with the potentialA difference between them when in operation, and a terminal connected to said block and projecting through the casing and insulated therefrom.

' 10. An electrical condenser comprising a central metal block; a plurality of stacks of sheets each of which stacks is short for heat conduction as compared with a single stack short stacks, whereby the latter are connected in parallel between the two condenser terminals.

11. An electrical condenser comprising a plurality of stacks of sheets, each stack be ing short for heat-conduction as compared with a single stack electrically equivalent to the, plural stacks; a common metal casing for said plural stacks, said casing being 1n good electrical and heat-conducting rela' tion with one set, of electrical ends of said plural stacks, and constituting one terminal of the condenser; and a heat-'conducting condenser connection in good electrical and heat-conducting relation with the other set ot electrical ends of said plurality of stacks, and'extending out through and insulated 'from said metal casing and constituting another terminal of the condenser.

1Q. 'ln an electrical condenser, a casing,

condenser elements Within the casing, a liller ot insulating material within the casing7 and means tor allowing the expansion ot said insulating material comprising a box-like member having a iiexible wall tacing the insulating material.

13. In an electrical condenser, a casing, condenser elements Within the casing, insulating material iilling said casing-'and surrounding said condenser elements, mea-ns for allowing the expansion and contraction of said insulating material comprising a. liexiblc diaphragm facing the insulatingmate- .rial and enclosing a chamber and a spring mounted in said chamber and engaging said diaphragm whereby it is resiliently supported.

14V. In an electrical condenser, a casing, a condenser stack mounted within the casing, said casing comprising a part of` the clamping means for the stack, insulating 15. An electrical condenser comprising a,

plurality oit' stacks of sheets', each stack'being short as compa-red with a single stack electrically equivalent to the plural stacks; members of high thermal conductivity in good thermal contact with opposite ends of said plural stacks; a common enclosure for said pluralstacks and heat-conducting members; and radiating members external to said ,enclosure and thermally connected with the thermal conducting members. 16. In an electrical condenser, a casing, condenser elements within'the casing, a filler ,of insulating material within the casing and means for `allowing the expansion of said insulating material comprising a box-like member attached 'to the casing and having an inner flexible diaphragm facing the filler and a spring in the box-like member bearing against said diaphragm. 17. In an electrical condenser, a casing, condenser elements within the casing, a iller of insulating material within the casing, said filler beinglplaced therein through an opening in the casing, and a-closure for said opening comprising a flexible diaphragm I the casing vand projecting ,therethrm and a large heat-radiating member mounted upon said terminal outside of the casing.

19. In an electrical condenser, a metal casing, a, stack therein, means for clamping the stackwithin the casing, "one end ot said stack being electrically connected to the casing, a hlgh potential `terminal connected to.

the opposite end of the stack and projecting thru said casing, an insulating bushing insulating said high potential terminal from the casing, a static shield mounted upon said terminal above said lbushing and eX- tending therearound to prevent losses there@ 1n, and a heat-radiating member of larger area than said shield and mounted on said terminal above ythe shield.

- 20. In an electrical condenser, a metal casing, four stacks arranged within said. casing and connected in parallel, .said stacks each comprising sections connected in series, each stack being relatively short compared to a single stack electrically equivalent to all of said stacks, a central block mounted within said casing with which the inner ends of the stacks engage and to which the stacks are electrically connected, said blocks having relatively high thermo-conductivity compared to the stacks, pressure members adjustably mounted on the casing and engaging the outer ends of the stacks whereby the casing, said terminal having high thermoconductivity compared to the stacks, a static shield mounted on said terminal above said bushing to prevent losses therein, a largeareaed heat-radiating member mounted upon said terminal above said shield, and a ller of insulating material within said casing surrounding said stack and the lower end of said terminal. y

21. In an electrical condenser, a metal casing, a central metal block mounted within the casing and having'a terminal projecting thru the casing and insulated therefrom, f our stacks mounted within the casing and `engaging said central block, adjacent stacks being arranged at an angle to each other, pressure members mounted on the casing and adjustably engaging said stacks for conipressing the same against the central member, the outer ends of said stacks being electrically connected to the casing to constitute a terminal thereof, the inner ends of the stacks being electrically connected to said block, said casing having reduced diameters intermediate the clamping means Land between adjacent staclrs and' being spaced from the adjacent sides of the stacks in accordance with the potential differences between them.

22. In an electrical condenser, a metal casing, a plurality of stacks horizontally'mounted in -said casing, a central pressure member with which the inner ends of the stacks engage and to which they are electrically connected, means engaging the outer ends of the stacks Lfor compressing them against the central member and adjusting the latter back and forth, the outer ends of the stacks being electrically connected to the casing, a rigid terminal threaded in said central member and projecting outside of the casing, means including a bushing for insulating said terminal from the casing and a metal member constituting a static shield for said bushing and for radiating heat and mounted on said terminal around said bushing.

23. In an electrical condenser, a metal casing, a plurality of stacks arranged horizontally within the casing, a common pressure member having high thermal conductivity compared to the thermal conductivity of the stacks and with which the stacks engage at their inner ends, pressure plates engaging the outer ends of the stacks, screws threaded in the casing and engaging the pressure plates for compressing the stacks against the common ressure member, said stacks being electrical y connected to the casing and central pressure member, a thermally conductive terminal electrically connected to said central member and projecting thru said casing and insulated therefrom and having outside of the casing a large heat-radiating surface and a llerlof insulating material within the casing.

24. In an electrical condenser, a metal casing, a plurality of stacks having a fall of potential therealong and arranged in spacedapart relation within the casing with their outer ends adjacent to and electrically connected to the casing, said casing having a reduced cross section between the stacks and extending between the same and spaced therefrom in accordance with the potential difference between the stacks and casing, and terminal means insulated from the casing for the inner ends of the stacks.

VILLIAM H. PRIESS. 

